OK that's your opinion and you may well be totally correct. However, your parents won't agree with you and if you don't attend your sister's wedding (wow, holding your tongue and smiling sweetly for all the world to see for one whole day.....shocking) you will REALLY upset them.....and, frankly, it will make you look like a spoiled brat who is jealous of her sister. Whether you are or not a jealous brat is of no consequence - THAT'S exactly what it will look like to EVERYONE else.....and then you will have to live with it and waste an awful lot of time convincing a lot of people that you aren't like that at all. In later years - bear in mind that sis is moving out of the house and you won't have to put up with her anymore - you might even grow to like her a bit. Just think, when you are 30 and she's showing off her wedding photos and you are nowhere to be seen, how are you going to reply to people when they ask why you are missing? You have to make a choice. Go to the wedding and be the best Oscar-winning-actress-on-the-planet for a whole day and get a quiet life.....or, don't go and get a shed-load of accusations, insults, hurt looks, tears and tantrums for a VERY long time. Up to you dear.